OSPF is a link-state protocol that enables neighbouring routers to share information
OSPF is a link-state protocol that enables neighbouring routers to share information and use it to improve efficiency in operation. This is done through its ability to develop a database know us the Link -State- Database which is made up of three tables:
- Neighbour Table: Contains all discovered OSPF neighbours with whom routing information will be interchanged
- Topology Table: Contains the entire road map of the network with all available OSPF routers and calculated best and alternative paths.
- Routing Table: Contain the current working best paths that will be used to forward data traffic between neighbours.
With the above database and its tables, the router’s interface running OSPF to advertise its link cost to its OSPF neighbours and neighbours will ensure synchronizing of this data to all routers. The routers will continuously update their link-state databases with information about the network topology and adjust their routing tables. For routers to be able to do this, they must be neighbours, and this is achieved if they are connected to the same subnet and share a series of standard configuration information including:
- Same Area ID
- Same Area type
- Same subnet mask
- Same timers
- Same authentication
And most importantly, they can see their own OSPF RID in each other’s Hello packet.